Scientific Name: Bilberry
Other Names: Airelle, Dyeberry, European Blueberry, Huckleberry, Vaccinium myrtillus, Whortleberry, Wineberry

Who is this for?

Uses

Currently, bilberry is probably best known for treating eye conditions. It has been shown in clinical studies to decrease some of the retinal damage caused by diabetes or high blood pressure in at least two ways. First, it contains chemicals known as anthocyanosides (or anthocyanins), which may increase retinal pigments (coloring agents) that allow the eye to tolerate light. Additionally, bilberry may help to make the walls of blood vessels in the eyes stronger by increasing collagen linkages. Collagen is a protein that supports and strengthens body structures such as skin and bones. As one result, retinopathy (the gradual break down of the retina in the eyes) may be slowed. Individuals with hardening of the arteries, diabetes, high blood pressure, or other conditions that increase the likelihood for damage to the small blood vessels in the eyes are more likely to have serious vision problems due to blood vessel damage. Note that bilberry is taken by mouth to treat eye problems. It is not used in eye drops.

Oral bilberry preparations are also used to prevent and treat weakened blood vessels. They are used extensively to relieve a condition known as chronic venous insufficiency, which occurs when valves in the veins that carry blood back to the heart are weak or damaged. Blood may collect in the veins of the legs and lead to varicose veins, spider veins, or sores on the legs. More serious results can include blood clots in the legs. Because bilberry may strengthen the walls of all blood vessels in the body, taking it may also relieve hemorrhoids. Some recent research may show that bilberry’s effect on blood vessels may also protect the heart and the coronary arteries from damage.

Bilberries contain tannins, although the actual tannin content may fluctuate between as little as 1.5% and as much as 10%. Drying bilberry fruits concentrates the tannins, so dried bilberries generally contain a higher percentage than fresh bilberries. In the past, dried bilberries have been used to treat diarrhea because the tannins act as an astringent to the gastrointestinal tract. An astringent shrinks and tightens the top layers of skin or mucous membranes, thereby reducing secretions, relieving irritation, and improving tissue firmness. Due to the same astringent effect, tea brewed from dried bilberry fruits has also been used to soothe a sore throat or sore mouth tissue. Recent laboratory studies show that bilberries also have an antibacterial effect, which may contribute to their antidiarrheal properties.

In folk medicine, bilberry leaf has been used to treat a number of conditions including diabetes. Limited evidence from a few animal studies shows that it may have a decreasing effect on blood sugar. Additionally, in at least one study, an extract of bilberry leaves may also have lowered cholesterol levels in laboratory animals. Other laboratory and animal studies have tested potential anticancer effects of bilberry. In a laboratory study, bilberry stopped the growth of both leukemia and colon cancer cells. While preliminary results suggest that anthocyanosides obtained from bilberries may also block the effects of an enzyme and other chemicals that promote tumor growth, much more study is needed. To date, no human clinical studies have confirmed any of these results from bilberry.

Precautions

Eating bilberry fruit seems to be safe during pregnancy and while breast-feeding, but no studies have been done to test the safety of supplemental doses of bilberry fruit or bilberry leaf products. Until more is known, supplemental bilberry is best avoided by pregnant and breast-feeding women.

Because bilberry may have a lowering effect on blood sugar, it may increase the effectiveness of medications used for the treatment of diabetes. Individuals who take medications for diabetes should talk to a doctor or pharmacist before using supplementary bilberry.

What side effects should I watch for?

Although no reports of major side effects from bilberry were found in the literature, other oral preparations that are high in tannin content have been associated with kidney or liver damage. Individuals with kidney or liver conditions should not take bilberry products.

A case study of several people who regularly used large amounts of an oral product containing high levels of tannins for many years, found they had a higher incidence of tongue and lip cancer than expected. Cancers of the nose and esophagus may also be more likely in people who use large amounts of tannin-containing products for long amounts of time.

What interactions should I watch for?

Prescription Drugs

The possible blood sugar-lowering effects of bilberry leaf may interfere with insulin and oral drugs for diabetes, such as:

• Actos
• Avandia
• glimepiride
• glipizide
• glyburide
• Glyset
• metformin
• Prandin
• Precose

Herbal Products

Because bilberry leaf may decrease blood sugar levels, taking it with other blood sugar-lowering herbal products may result in hypoglycemia—blood sugar that is too low. Herbals that may reduce blood sugar include:

• Eleuthero
• Fenugreek
• Ginger (in high amounts)
• Kudzu
• Panax ginseng

Foods

Although no interactions have been reported between bilberry and foods, the tannins in bilberry may interfere with the absorption of minerals such as calcium, iron, and magnesium from foods. A dietary deficiency of these minerals is very rare in the United States, but it might be possible if very large amounts of bilberry are used.

No other interactions have been reported between bilberry and prescription drugs, non-prescription drugs, other herbal supplements, or foods. However, because few reliable studies of bilberry have been conducted, its possible interactions with drugs, foods, and other dietary supplements are not understood completely. Other oral products that contain tannins have interfered with the way the body uses certain drugs. A doctor or pharmacist should be aware of all the prescription and non-prescription medicines being taken before an individual begins to use bilberry or any other herbal supplement.

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how bilberry interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.

Should I take it?

Closely related to blueberries, bilberries are believed to be native to Northeastern Europe. A small perennial bush, bilberry bears white or pinkish flowers late in the spring. The leaves are quite attractive—during the growing season they are a light green or green-yellow that becomes a reddish color in the autumn. Both the flowers and the leaves are waxy in appearance. Numerous wrinkled, dark blue or black berries that resemble blueberries in size and shape ripen in the autumn. Although they are cultivated as a crop in some countries of Eastern Europe, most bilberries grow wild in damp woodlands and marsh edges. In Britain and Europe, the bushes are often used in landscaping.

Like other berries, bilberry fruits are harvested and used for cooking, baking, and making jams. Dried bilberries are used like raisins. They have a slightly sour taste more similar to cranberries than blueberries. In earlier times, bilberries were added to wine to give it color. They were also used to prevent scurvy, a condition caused by vitamin C deficiency. Both the fruits and, less frequently, the leaves of bilberry are used in medicine. Ripe bilberries are collected and dried; bilberry leaves are harvested and dried before they begin to color in the fall.

Dosage and Administration

Bilberry is available in commercial oral dosage forms such as capsules, extracts, and tablets. It is often sold in combination with other herbals such as eyebright or supplements such as beta-carotene that also may enhance vision. Each of these products has various strengths and different recommendations for dosing. Individuals who decide to use one of them should follow the directions on the package that is bought.

A tea may be made from either dried bilberries or dried bilberry leaves. No limits are suggested for the maximum amount of tea per day, but continual use for more than a few days at a time is discouraged because of the tannin content.

• To make bilberry fruit tea about 2 teaspoons of dried bilberries should be allowed to soften for several minutes or longer in about 5 ounces of cold water. The water should then be heated but not boiled for about 10 minutes. The bilberries should be removed before drinking the tea, but they may be eaten or used in cooking, if desired.
• For bilberry leaf tea, about 2 teaspoons of chopped dried bilberry leaf should be soaked in about 5 ounces of boiling water for about 10 minutes. The solid particles should be strained out before drinking the tea.

Summary

Bilberries may be taken by mouth to treat retinopathy, chronic venous insufficiency, hemorrhoids, and other conditions that are associated with the deterioration of small blood vessels. They may also help to relieve diarrhea and sore throats. Leaves from the bilberry bush may also have some medicinal effects, but they have not been studied as much as the possible effects of the berries.

Risks

Bilberry contains varying amounts of chemicals known as tannins, which have been associated with kidney or liver damage. While eating small amounts of bilberries as part of the diet appears to be safe, consuming large amounts or continually taking supplemental bilberry should be avoided by pregnant women and individuals with diabetes.

Side Effects

Other oral products that contain high percentages of tannins may contribute to esophageal or mouth cancer. Kidney and liver damage may also result from continued use or high doses of oral products with high tannin contents.

Interactions

Bilberry may interfere with the effectiveness of insulin, oral drugs for diabetes, and herbal products that affect blood sugar levels. It may also block the absorption of some drugs and nutrients.

Last Revised July 31, 2007

References

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Last Revised July 31, 2007

Note: The above information is not intended to replace the advice of your physician, pharmacist, or other healthcare professional. It is not meant to indicate that the use of the product is safe, appropriate, or effective for you.

In general, herbal products are not subject to review or approval by the U.S. Food and Drug Administration (FDA). They are not required to be standardized, meaning that the amounts of active ingredients or contaminants they contain may vary between brands or between different batches of the same brand. Not all of the risks, side effects, or interactions associated with the use of herbal products are known because few reliable studies of their use in humans have been done.

This information is provided for your education only. Please share this information with your healthcare provider and be sure that you talk to your doctor and pharmacist about all the prescription and non-prescription medicines you take before you begin to use any herbal product.

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